Synthesis of polysaccharide derivatives bearing bromobenzoate pendants for use as chiral auxiliaries

Cellulose and amylose derivatives bearing bromobenzoate pendants were synthesized as chiral auxiliaries to create optically active biaryl compounds through Suzuki-Miyaura cross-coupling with naphthalen-1-ylboronic acids. The regioselectively substituted polysaccharide derivatives bearing 2-bromobenzoate pendants at the 6-position of the glucose unit exhibited higher diastereoselectivity than did the corresponding monosaccharide-based chiral auxiliary and the non-regioselectively substituted polysaccharide derivative bearing 2-bromobenzoates at the 2,3,6-positions. These results suggest that the chiral induction by the regioselectively substituted polysaccharide-based auxiliaries is mainly based on regular higher-order structures, such as one-handed helical structures.